The present invention relates to valves employed for controlling the venting of fuel vapors from a motor vehicle fuel tank during refueling or tank filling and are sometimes known as onboard refueling vapor recovery valves (or ORVR valves). Such valves control the venting of fuel vapor during tank filling, typically through a separate filler neck in the fuel tank, where the valve is connected to control flow of vapor from the tank vent to a recovery trap such as a charcoal filled storage canister which can be purged by connection to the engine intake manifold during engine operation.
Such fuel vapor recovery systems are widely employed in passenger and light truck motor vehicles which use highly volatile hydrocarbon fuel such as gasoline to prevent escape of fuel vapor to the atmosphere during refueling and periods of engine shut down.
Heretofore, known ORVRs have employed a float operated poppet or valve which closes a first stage or larger diameter vent passage during filling when the fuel in the tank reaches a level where the portion of the liquid fuel is greater than the portion of vapor. A second float operated valve is employed to close a secondary smaller vent passage which permits venting therethrough while the fuel level continues thereafter to rise and is closed when the fuel level reaches the top of the tank. Examples of this type of ORVR are shown and described in U.S. Pat. No. 5,590,697 which discloses a two-stage ORVR wherein the second smaller passage is formed through the poppet and the second valve is operated by the same float as the poppet.
Referring to FIGS. 3 and 4, a valve assembly of the prior art is shown as having a valve body 1, having a lower portion 2 received through an aperture 3 in the top wall 4 of a fuel tank and the body has a fuel vapor recovery vent port 5 which is adapted for connection to a fuel vapor storage canister 6 which is typically connected to the engine inlet manifold 7.
The body is typically sealed in the top wall of the tank by a resilient seal ring 8; and, the lower portion 2 has a passage 9 communicating downwardly from the port 5 to a valve seating shoulder 10 formed therein which forms the upper end of a hollow chamber 11 which has a float 12 disposed therein. The float is typically biased in the direction of buoyancy by a calibration spring 13.
The float 12 has thereon a poppet subassembly indicated generally at 14 which has a second stage reduced diameter vent passage 15 formed therethrough and has a flexible elastomeric seal 16 received thereover on the upper surface of the inverted cup-shaped member 17 for sealing against the sealing surface 10 thereby closing first stage vent passage 9. Member 17 is retained on float 12, in telescoping lost motion arrangement by a cage member 12a secured to the float 72. A secondary valve member 18 is disposed on the upper surface of the float 12 and is moved upwardly by continued movement of the float after seal 16 has closed the passage 9 by virtue of the telescoping of the cup-shaped member 17 within cage 12a.
The cup 17 has a second annular flexible elastomeric seal lip 19 provided on the inner surface of the upper closed end thereof for sealing on the surface of valve 18.
In operation, the tank 4 is filled with fuel through a filler neck (not shown) and the fuel vapor is displaced outwardly through port 5 to the canister 6 by the rising level of liquid fuel in the tank. Upon the liquid fuel reaching a predetermined level, typically more than the majority of the capacity of the tank, float 12 causes the poppet 14 to move upwardly closing seal 16 on seat 10 to close off the large flow area to passage 9. As liquid fuel is continued thereafter to be added to the tank, vapor is vented through cross ports 20 in the member 14 and through the reduced diameter vent passage 15 until the capacity of the tank is reached wherein the float 12 causes valve member 18 to seat against the seal lip 19 and close off vent passage 15. Thus, a two-stage venting of the fuel vapor to the canister during filling is effected.
The poppet assembly has the upper resilient seal 16 secured on the cup 17 by a separate cap member 21 received over the upper end of the cup 17 and snap locked thereon, thus forming a four piece assembly of the flexible seals 16, 19, the cup 17 and the cap 21.
In such arrangements, the valve closing forces available are quite minimal due to the low density or specific gravity of the fuel and the small displacement of the float. Therefore, in the aforesaid known valve constructions resiliently flexible seals have been required to seal the first stage poppet about the larger vent passage and the second valve member about the smaller vent passage. This requirement has resulted in added complexity to the valve design by virtue of requiring separate resiliently flexible seals; and, additional parts are required in assembly to retain such seals in the valve during manufacturing. This has resulted in additional parts and a relatively high manufacturing cost and assembly problems during manufacturing. Therefore, it has long been desired to provide a way or means of making a two-stage ORVR which can seal the vent ports reliably with float buoyancy forces and which is robust and relatively low in manufacturing cost for high volume automotive applications.